Re: [patch V4 06/15] x86/irq: Move IOAPIC misrouted and PIC/APIC error counts into irq_stats

[Radu Rendec <radu@rendec.net>]

On Tue, 2026-03-31 at 09:25 +0200, Thomas Gleixner wrote:
> From: Thomas Gleixner <tglx@kernel.org>
> 
> The special treatment of these counts is just adding extra code for no real
> value. The irq_stats mechanism allows to suppress output of counters, which
> should never happen by default and provides a mechanism to enable them for
> the rare case that they occur.
> 
> Move the IOAPIC misrouted and the PIC/APIC error counts into irq_stats,
> mark them suppressed by default and update the sites which increment them.
> 
> This changes the output format of 'ERR' and 'MIS' in case there are events
> to the regular per CPU display format and otherwise suppresses them
> completely.
> 
> As a side effect this removes the arch_cpu_stat() mechanism from proc/stat
> which was only there to account for the error interrupts on x86 and missed
> to take the misrouted ones into account.
> 
> Signed-off-by: Thomas Gleixner <tglx@kernel.org>
> ---
> V3: New patch
> ---
>  arch/x86/include/asm/hardirq.h |    7 ++++---
>  arch/x86/include/asm/hw_irq.h  |    4 ----
>  arch/x86/kernel/apic/apic.c    |    2 +-
>  arch/x86/kernel/apic/io_apic.c |    4 +---
>  arch/x86/kernel/i8259.c        |    2 +-
>  arch/x86/kernel/irq.c          |   16 ++++------------
>  fs/proc/stat.c                 |    4 ----
>  7 files changed, 11 insertions(+), 28 deletions(-)
> --- a/arch/x86/include/asm/hardirq.h
> +++ b/arch/x86/include/asm/hardirq.h
> @@ -50,6 +50,10 @@ enum irq_stat_counts {
>  #ifdef CONFIG_X86_POSTED_MSI
>  	IRQ_COUNT_POSTED_MSI_NOTIFICATION,
>  #endif
> +	IRQ_COUNT_PIC_APIC_ERROR,
> +#ifdef CONFIG_X86_IO_APIC
> +	IRQ_COUNT_IOAPIC_MISROUTED,
> +#endif
>  	IRQ_COUNT_MAX,
>  };
>  
> @@ -81,9 +85,6 @@ extern void ack_bad_irq(unsigned int irq
>  #ifdef CONFIG_PROC_FS
>  extern u64 arch_irq_stat_cpu(unsigned int cpu);
>  #define arch_irq_stat_cpu	arch_irq_stat_cpu
> -
> -extern u64 arch_irq_stat(void);
> -#define arch_irq_stat		arch_irq_stat
>  #endif
>  
>  DECLARE_PER_CPU_CACHE_HOT(u16, __softirq_pending);
> --- a/arch/x86/include/asm/hw_irq.h
> +++ b/arch/x86/include/asm/hw_irq.h
> @@ -110,10 +110,6 @@ static inline void lock_vector_lock(void
>  static inline void unlock_vector_lock(void) {}
>  #endif
>  
> -/* Statistics */
> -extern atomic_t irq_err_count;
> -extern atomic_t irq_mis_count;
> -
>  extern void elcr_set_level_irq(unsigned int irq);
>  
>  extern char irq_entries_start[];
> --- a/arch/x86/kernel/apic/apic.c
> +++ b/arch/x86/kernel/apic/apic.c
> @@ -2180,7 +2180,7 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_error_inte
>  		apic_write(APIC_ESR, 0);
>  	v = apic_read(APIC_ESR);
>  	apic_eoi();
> -	atomic_inc(&irq_err_count);
> +	irq_stat_inc_and_enable(IRQ_COUNT_PIC_APIC_ERROR);
>  
>  	apic_pr_debug("APIC error on CPU%d: %02x", smp_processor_id(), v);
>  
> --- a/arch/x86/kernel/apic/io_apic.c
> +++ b/arch/x86/kernel/apic/io_apic.c
> @@ -1575,8 +1575,6 @@ static unsigned int startup_ioapic_irq(s
>  	return was_pending;
>  }
>  
> -atomic_t irq_mis_count;
> -
>  #ifdef CONFIG_GENERIC_PENDING_IRQ
>  static bool io_apic_level_ack_pending(struct mp_chip_data *data)
>  {
> @@ -1713,7 +1711,7 @@ static void ioapic_ack_level(struct irq_
>  	 * at the cpu.
>  	 */
>  	if (!(v & (1 << (i & 0x1f)))) {
> -		atomic_inc(&irq_mis_count);
> +		irq_stat_inc_and_enable(IRQ_COUNT_IOAPIC_MISROUTED);
>  		eoi_ioapic_pin(cfg->vector, irq_data->chip_data);
>  	}
>  
> --- a/arch/x86/kernel/i8259.c
> +++ b/arch/x86/kernel/i8259.c
> @@ -214,7 +214,7 @@ static void mask_and_ack_8259A(struct ir
>  			       "spurious 8259A interrupt: IRQ%d.\n", irq);
>  			spurious_irq_mask |= irqmask;
>  		}
> -		atomic_inc(&irq_err_count);
> +		irq_stat_inc_and_enable(IRQ_COUNT_PIC_APIC_ERROR);
>  		/*
>  		 * Theoretically we do not have to handle this IRQ,
>  		 * but in Linux this does not cause problems and is
> --- a/arch/x86/kernel/irq.c
> +++ b/arch/x86/kernel/irq.c
> @@ -39,8 +39,6 @@ EXPORT_PER_CPU_SYMBOL(__softirq_pending)
>  
>  DEFINE_PER_CPU_CACHE_HOT(struct irq_stack *, hardirq_stack_ptr);
>  
> -atomic_t irq_err_count;
> -
>  /*
>   * 'what should we do if we get a hw irq event on an illegal vector'.
>   * each architecture has to answer this themselves.
> @@ -124,6 +122,10 @@ static const struct irq_stat_info irq_st
>  #ifdef CONFIG_X86_POSTED_MSI
>  	ISS(POSTED_MSI_NOTIFICATION,	"PMN", "  Posted MSI notification event\n"),
>  #endif
> +	IDS(PIC_APIC_ERROR,		"ERR", "  PIC/APIC error interrupts\n"),
> +#ifdef CONFIG_X86_IO_APIC
> +	IDS(IOAPIC_MISROUTED,		"MIS", "  Misrouted IO/APIC interrupts\n"),
> +#endif
>  };
>  
>  static DECLARE_BITMAP(irq_stat_count_show, IRQ_COUNT_MAX) __read_mostly;
> @@ -183,10 +185,6 @@ int arch_show_interrupts(struct seq_file
>  		irq_proc_emit_counts(p, &irq_stat.counts[i]);
>  		seq_puts(p, info->text);
>  	}
> -
> -	seq_printf(p, "%*s: %10u\n", prec, "ERR", atomic_read(&irq_err_count));
> -	if (IS_ENABLED(CONFIG_X86_IO_APIC))
> -		seq_printf(p, "%*s: %10u\n", prec, "MIS", atomic_read(&irq_mis_count));
>  	return 0;
>  }
>  
> @@ -202,12 +200,6 @@ u64 arch_irq_stat_cpu(unsigned int cpu)
>  		sum += p->counts[i];
>  	return sum;
>  }
> -
> -u64 arch_irq_stat(void)
> -{
> -	u64 sum = atomic_read(&irq_err_count);
> -	return sum;
> -}
>  #endif /* CONFIG_PROC_FS */
>  
>  static __always_inline void handle_irq(struct irq_desc *desc,
> --- a/fs/proc/stat.c
> +++ b/fs/proc/stat.c
> @@ -18,9 +18,6 @@
>  #ifndef arch_irq_stat_cpu
>  #define arch_irq_stat_cpu(cpu) 0
>  #endif
> -#ifndef arch_irq_stat
> -#define arch_irq_stat() 0
> -#endif
>  
>  u64 get_idle_time(struct kernel_cpustat *kcs, int cpu)
>  {
> @@ -122,7 +119,6 @@ static int show_stat(struct seq_file *p,
>  			sum_softirq += softirq_stat;
>  		}
>  	}
> -	sum += arch_irq_stat();
>  
>  	seq_put_decimal_ull(p, "cpu  ", nsec_to_clock_t(user));
>  	seq_put_decimal_ull(p, " ", nsec_to_clock_t(nice));

Reviewed-by: Radu Rendec <radu@rendec.net>